Bolsters and the like are known in the art. A conventional bolster is mounted within a passenger compartment and includes a hollow body and an inflator for injecting a pressurized fluid into the hollow body. In order to reduce the potential for injuries caused during an impact event or the like, the inflator is activated upon detection of such an event and the bolster is inflated.
For example, the impact event may be a front, rear or side impact, a rollover, or any other event which is likely to cause a rapid change in the vehicle's momentum and thereby cause the occupant to strike some portion of the vehicle's passenger compartment. The fluid released by the inflator into the hollow body serves to inflate the bolster, bringing its outer surface closer to an occupant. By decreasing the distance between the occupant and its outer surface, the bolster can absorb more of the occupant's momentum over a longer period of time, thereby lessening the force experienced.
Bolsters may be provided as part of an instrument panel, a door panel, roof panel, a head rest, or other interior portion of the vehicle.
With reference to FIG. 1, an inflatable bolster 10 including several aspects of a conventional bolster is illustrated for exemplification purposes. In this example, a first wall 12 is mounted to the vehicle and a second wall 14 is exposed, facing the vehicle's passenger compartment. An inflator 18 is mounted to the bolster 10, which here is shown in an uninflated state.
In order to increase the volume of the inflated bolster 10, it is known to provide a plurality of pleats 18 formed in one of the first and second walls 12 and 14. When uninflated, the pleats 18 are folded and form a wave-like pattern as shown, for example, in FIG. 1A. During inflation, the pleats 18 can unfold and the bolster 10 is able to expand outward.
It has been found however that when such bolsters are in their folded, stored position, they can create a hollow sound when an occupant, for example, knocks, scrapes, touches, or otherwise makes contact with the wall facing the passenger compartment. It will be appreciated that a bolster's hollow body can behave somewhat like sound box and that a generally flat occupant facing wall may behave somewhat like a drum skin. Moreover, the occupant facing wall may be deflected inward, towards the opposing wall, and create a popping sound when released. Alternatively, as the vehicle, and hence the bolsters therewithin, vibrates, this can create a rattling sound. In addition, it will be appreciated that air holes in the bolster 10 could be another source of unwanted noise.
It will be appreciated that these unwanted acoustical effects can be irritating, distracting and/or give an impression of low quality. In addition, it will be appreciated that any crack in the surface finish or otherwise which might result from these unwanted vibrations could be undesirable.
It is known to stiffen bolsters by providing them with ribs which extend longitudinally across the bolster's body.
For example, U.S. Pat. No. 6,619,689 discloses a bolster having a pair of transverse strengthening ribs which are formed in an inner wall. These strengthening ribs extend inwards of the bolster's hollow body and engage an opposing outer wall.
It will be appreciated however that these while ribs strengthen the bolster, they will have little to no effect on the acoustical behavior of the bolster. The strengthening ribs engage the outer wall along two lines which extend across the center of the bolster. There remain, however, two large sections on either side of the ribs which may still create unwanted noise.
Also known in the art are the following patent and patent applications which disclose inflatable bolsters and the like: US 2007/0108747; U.S. Pat. Nos. 6,032,978; 6,203,057; 6,305,710; 6,517,103; 6,578,867; 6,758,493; 6,848,715; 6,976,706; 7,350,852; and WO 2006/132990.
None of these prior art patents adequately address the above-noted problems.
It would therefore be advantageous to provide an inflatable bolster which at least partially prevented such unwanted acoustical effects.